Control slump and moisture in your product by measuring the raw materials
Four moisture meters for different applications
Moisture measurement is an inexact science. The reason for this is the measurement zone, which is an area of a few square inches. Compared with the area of a typical feed gate in a bin, with an area of 150 to 350 square inches, it is very small. Consequently, aggregates falling from one side of the bin or another, with different moisture values, can escape inclusion in the average. Also, different moisture sensor types are best suited to different materials and environments, as detailed below.
You need to do three things to guarantee success:
- Hold density constant, since all sensors are density sensitive. This is accomplished by placement in a bin and angling the sensing faceplate to slow and compact the material as it flows past.
- Make the measurement within the flow region, above the feed gate in a bin; not in the side where material does not flow.
- Average the readings while the material is flowing. The average must be held between batches.
You should install your moisture probe in a bin or hopper where the material is compacted because this gives reliable density and therefore the most accurate moisture measurement. Also, smaller granule size, compared with the measurement aperture, gives higher accuracy. We offer three types of sensor for different environments:
AquaSense is the best choice for measuring the moisture of sand and granular materials, fine aggregates (up to 1/4″ or 6 mm) or similar products that can be compacted inside a bin or hopper. The material flows past the moisture sensor and the result is averaged during the flow period. This gives a better average than obtained from oven-dry tests. It can also be used in a ‘ski’ fixture that rides on top of a thick bed of material on a conveyor belt. This, however, gives reduced accuracy.
AquaSense is the ONLY moisture sensor with a 10 year guarantee!
For use in mixers for concrete and similar applications, AquaMix uses the hardest known material after diamond, Silicon Nitride, for its faceplate. Due to this, a life of over 10 years is typical in moisture measurement of extreme aggregates such as granite used daily in mixing of concrete. The moisture sensor is embedded in the floor of pan, ribbon or twin-shaft mixers. A fixture is used to allow adjustment for the wear of the liner plates. Both AquaSense and AquaMix use the same setup and calibration software. If widely different blends of material are to be mixed (for example lightweight and regular block mixes), up to 10 different sets of calibration values can be stored in the sensor.
If a batch controller is not used or does not have mixer moisture software, AquaControl controls the addition of water, based on readings from the AquaMix sensor. It connects to the moisture probe, water valves and meter. The controller is based on the same combination of PLC and touch screen used in BatchTron models. Because of this, three different methods are available to measure and add the water, depending on the application:
- MicroMix, a simple, calibration-free method that does not require a water meter.
- Fast MicroMix, which requires a water meter but improves speed by predicting the amount of fast pre-water to be added.
- MasterMix, which requires a water meter plus accurate sensor calibration but gives the ultimate speed and accuracy.
This moisture sensor uses near-infrared light to measure the surface moisture of sand, aggregates and other granular materials as they pass by on a belt or flow out of a hopper. Polarmoist is the only system that can measure the surface moisture of large aggregates (greater than 3/8″ or 10 mm). Capacitance and microwave moisture meters show too much variation. Because this method measures the surface of the material, it is not density sensitive. Polarmoist is not a Scale-Tron manufactured item. It is available for these special applications or where clients prefer the IR sensing method.